Primary hyperoxaluria type 1: is genotyping clinically helpful?

Abstract

There is some controversy about the value of mutation analysis in the management of primary hyperoxaluria type 1 (PH1). About 50 different mutations of the AGXT gene encoding the liver-specific peroxisomal enzyme alanine:glyoxylate aminotransferase (AGT) are currently known. The three most common mutations in the Western population account for less than half of the mutant alleles, and no simple screening test is available. Does the genotype help in diagnosis, prognosis and therapy? Definitive diagnosis is indispensable if liver transplantation is considered and can under certain circumstances be established by mutation analysis, but a liver biopsy is still necessary to determine AGT activity in a number of cases. Prognosis is difficult to assess due to a large clinical variation, despite identical mutations. Although the homozygous 508G>A (Gly170Arg) mutation appears to be associated with a better (and 33insC with a worse) prognosis, there are too many exceptions for precise prediction. Pyridoxine responsiveness can be anticipated in some genotypes (508G>A (Gly170Arg) and 454T>A (Phe153Ile)), but it should still be tested for in all patients. Genetic testing is thus clinically helpful but has clear limitations.